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Antarctica, on average, is the coldest, driest, and windiest continent, and has the highest average
elevation
of all the continents.[6]
Antarctica is considered a desert, with annual
precipitation
of only 200 mm (8 inches) along the coast and far less inland.[7]
The temperature in Antarctica has reached −89 °C (−129 °F). There are no permanent human residents, but anywhere from 1,000 to 5,000 people reside throughout the year at the research stations scattered across the continent. Only cold-adapted organisms survive, including many types of algae,
bacteria,
fungi,
plants,
protista, and certain
animals, such as
mites,
nematodes,
penguins,
seals
and tardigrades. Vegetation where it occurs is
tundra.

Antarctica is a
de factocondominium, governed by parties to the
Antarctic Treaty System
that have consulting status. The Antarctic Treaty
was signed in 1959 by 12 countries; to date, 50 countries have signed the treaty. The treaty prohibits military activities and mineral mining, prohibits nuclear explosions and nuclear waste disposal, supports scientific research, and protects the continent's ecozone. Ongoing experiments are conducted by more than 4,000 scientists from many nations.

The name
Antarctica
is the romanized
version of the Greek
compound word ἀνταρκτική
(antarktiké), feminine of
ἀνταρκτικός
(antarktikos),[8]
meaning "opposite to the Arctic", "opposite to the north".[9]

Before getting its present geographical connotations, the term was used for other locations that could be defined as "opposite to the north". For example, the short-lived French colony established at
Brazil
in the 16th century was called "France Antarctique".

Antarctica has no indigenous population and there is no evidence that it was seen by humans until the 19th century. However, belief in the existence of a
Terra Australis—a vast continent in the far south of the globe to "balance" the northern lands of Europe, Asia and
North Africa—had existed since the times of
Ptolemy
(1st century AD), who suggested the idea to preserve the symmetry
of all known landmasses
in the world. Even in the late 17th century, after explorers had found that South America and Australia were not part of the fabled "Antarctica", geographers believed that the continent was much larger than its actual size.

Painting of James Weddell's second expedition in 1823, depicting the brig
Jane
and the cutter Beaufroy.

Integral to the story of the origin of the name "Antarctica" is how it was not named
Terra Australis—this name was given to Australia instead, and it was because of a mistake made by people who decided that a significant landmass would not be found further south of Australia. Explorer
Matthew Flinders, in particular, has been credited with popularizing the transfer of the name
Terra Australis
to Australia. He justified the titling of his book A Voyage to Terra Australis
(1814) by writing in the introduction:

There is no probability, that any other detached body of land, of nearly equal extent, will ever be found in a more southern latitude; the name Terra Australis will, therefore, remain descriptive of the geographical importance of this country, and of its situation on the globe: it has antiquity to recommend it; and, having no reference to either of the two claiming nations, appears to be less objectionable than any other which could have been selected.[11]

(For more information about how Australia was named after
Terra Australis
instead of Antarctica, see Australia#Etymology.)

Richard E. Byrd
led several voyages to the Antarctic by plane in the 1930s and 1940s. He is credited with implementing mechanized land transport on the continent
and conducting extensive geological and biological research.[29]
However, it was not until 31 October 1956 that anyone set foot on the South Pole again; on that day a U.S. Navy group led by Rear Admiral George J. Dufek
successfully landed an aircraft there.[30]

The first person to sail single-handed to Antarctica was the New Zealander
David Henry Lewis, in 1972, in a 10-metre steel sloop
Ice Bird.

Positioned asymmetrically around the
South Pole
and largely south of the Antarctic Circle, Antarctica is the southernmost continent and is surrounded by the Southern Ocean; alternatively, it may be considered to be surrounded by the southern
Pacific,
Atlantic, and Indian Oceans, or by the southern waters of the
World Ocean. It covers more than 14,000,000 km2
(5,400,000 sq mi),[1]
making it the fifth-largest continent, about 1.3 times as large as Europe. The coastline measures 17,968 km (11,165 mi)[1]
and is mostly characterized by ice formations, as the following table shows:

Antarctica is divided in two by the
Transantarctic Mountains
close to the neck between the Ross Sea and the Weddell Sea. The portion west of the Weddell Sea and east of the Ross Sea is called West Antarctica and the remainder East Antarctica, because they roughly correspond to the Western and Eastern Hemispheres relative to the
Greenwich meridian.

Elevation colored by relief height

About 98% of Antarctica is covered by the
Antarctic ice sheet, a
sheet of ice
averaging at least 1.6 km (1.0 mi) thick. The continent has about 90% of the world's ice (and thereby about 70% of the world's fresh water). If all of this ice were melted, sea levels would rise about 60 m (200 ft).[32]
In most of the interior of the continent, precipitation
is very low, down to 20 mm (0.8 in) per year; in a few "blue ice" areas precipitation is lower than mass loss by
sublimation
and so the local mass balance is negative. In the dry valleys, the same effect occurs over a rock base, leading to a desiccated landscape.

Vinson Massif, the highest peak in Antarctica at 4,892 m (16,050 ft), is located in the
Ellsworth Mountains. Antarctica contains
many other mountains, on both the main continent and the surrounding islands. Mount Erebus on
Ross Island
is the world's southernmost active volcano. Another well-known volcano is found on Deception Island, which is famous for a giant eruption in 1970. Minor eruptions are frequent and lava flow has been observed in recent years. Other dormant volcanoes may potentially be active.[33]
In 2004, an underwater volcano was found in the Antarctic Peninsula
by American and Canadian researchers. This unnamed volcano may be active.[34]

Antarctica is home to more than 70 lakes that lie at the base of the continental ice sheet.
Lake Vostok, discovered beneath Russia's
Vostok Station
in 1996, is the largest of these subglacial lakes. It was once believed that the lake had been sealed off for 500,000 to one million years but a recent survey suggests that, every so often, there are large flows of water from one lake to another.[35]

There is some evidence, in the form of
ice cores
drilled to about 400 m (1,300 ft) above the water line, that Lake Vostok's waters may contain microbial life. The frozen surface of the lake shares similarities with
Jupiter's moon,
Europa. If life was discovered in Lake Vostok, it would strengthen the argument for the possibility of life on Europa.[36]
On 7 February 2008, a NASA team embarked on a mission to Lake Untersee, searching for
extremophiles
in its highly alkaline waters. If found, these resilient creatures could further bolster the argument for extraterrestrial life in extremely cold, methane-rich environments.[37]

The above map shows the subglacial topography of Antarctica. As indicated by the scale on left-hand side, blue represents portion of Antarctica lying below sea level. The other colors indicate Antarctic bedrock lying above sea level. Each color represents an interval of 2,500 ft (760 m) in elevation. Map is not corrected for sea level rise or isostatic rebound, which would occur if the Antarctic ice sheet completely melted to expose the bedrock surface.

Topographic map of Antarctica after removing the ice sheet and accounting for both isostatic rebound and sea level rise. Hence, this map suggests what Antarctica may have looked like 35 million years ago, when the Earth was warm enough to prevent the formation of large-scale ice sheets in Antarctica.

More than 170 million years ago, Antarctica was part of the
supercontinentGondwana. Over time, Gondwana gradually broke apart and Antarctica as we know it today was formed around 25 million years ago. Antarctica was not always cold, dry, and covered in ice sheets. At a number of points in its long history, it was farther north, experienced a tropical or temperate climate, was covered in forests, and inhabited by various ancient life forms.

During the
Cambrian period, Gondwana had a mild climate. West Antarctica was partially in the
Northern Hemisphere, and during this period large amounts of
sandstones,
limestones
and shales
were deposited. East Antarctica was at the equator, where sea floor invertebrates
and trilobites
flourished in the tropical seas. By the start of the Devonian period
(416 Ma), Gondwana was in more southern latitudes and the climate was cooler, though fossils of land plants are known from this time.
Sand
and silts
were laid down in what is now the Ellsworth,
Horlick
and Pensacola Mountains.
Glaciation
began at the end of the Devonian period (360 Ma), as Gondwana became centered around the South Pole and the climate cooled, though flora
remained. During the Permian
period, the plant life became dominated by fern-like plants such as
Glossopteris, which grew in swamps. Over time these swamps became deposits of coal in the
Transantarctic Mountains. Towards the end of the Permian period, continued warming led to a dry, hot climate over much of Gondwana.[38]

As a result of continued warming, the polar ice caps melted and much of Gondwana became a desert. In Eastern Antarctica,
seed ferns
became established, and large amounts of sandstone and shale were laid down at this time. Synapsids, commonly known as "mammal-like reptiles", were common in Antarctica during the
Late Permian
and Early Triassic
and included forms such as Lystrosaurus. The Antarctic Peninsula began to form during the
Jurassic
period (206–146 Ma), and islands gradually rose out of the ocean. Ginkgo
trees and cycads
were plentiful during this period. In West Antarctica, coniferousforests
dominated through the entire Cretaceous
period (146–66 Ma), though Southern beech
became more prominent towards the end of this period. Ammonites
were common in the seas around Antarctica, and dinosaurs were also present, though only three Antarctic dinosaur genera
(Cryolophosaurus
and Glacialisaurus, from the
Hanson Formation,[39]
and Antarctopelta) have been described to date.[40]
It was during this period that Gondwana began to break up.

The cooling of Antarctica occurred stepwise, as the continental spread changed the oceanic currents from longitudinal equator-to-pole temperature-equalizing currents to latitudinal currents that preserved and accentuated latitude temperature differences.

Africa separated from Antarctica around 160 Ma, followed by the
Indian subcontinent, in the early Cretaceous (about 125 Ma). By the end of the Cretaceous, about 66 Ma, Antarctica (then connected to Australia) still had a tropical to subtropical climate, complete with a
marsupialfauna. About 40 Ma Australia-New Guinea
separated from Antarctica, so that latitudinal currents could isolate Antarctica from Australia, and the first ice began to appear. During the Eocene–Oligocene extinction event
about 34 million years ago, CO2
levels have been found to be about 760 ppm[41]
and had been decreasing from earlier levels in the thousands of ppm.

Around 23 Ma, the
Drake Passage
opened between Antarctica and South America, resulting in the Antarctic Circumpolar Current
that completely isolated the continent. Models of the changes suggest that declining CO2
levels became more important.[42]
The ice began to spread, replacing the forests that then covered the continent.

Since about 15 Ma, the continent has been mostly covered with ice.[43]

Fossil
Nothofagus
leaves in the Meyer Desert Formation of the Sirius Group
show that intermittent warm periods allowed Nothofagus
shrubs to cling to the Dominion Range
as late as 3–4 Ma.[44]
After that the Pleistocene
ice-age covered the whole continent and destroyed all major plant life on it.[45]

H.M. Li and Z.K. Zhou (2007)
Fossil nothofagaceous leaves from the Eocene of western Antarctica and their bearing on the origin, dispersal and systematics of Nothofagus.
Science in China. 50(10): 1525-1535.

Glaciers and rock outcrops in Marie Byrd Land seen from NASA's DC-8 aircraft

The geological study of Antarctica has been greatly hindered by the fact that nearly all of the continent is permanently covered with a thick layer of ice.[46]
However, new techniques such as remote sensing,
ground-penetrating radar
and satellite imagery
have begun to reveal the structures beneath the ice.

Antarctica is the coldest of
Earth's continents. The coldest natural temperature ever recorded on Earth was −89.2 °C (−128.6 °F) at the Soviet (now
Russian)
Vostok Station
in Antarctica on 21 July 1983.[47]
For comparison, this is 11 °C (20 °F) colder than sublimingdry ice
at one atmosphere of partial pressure, but since CO2
only makes up 0.039% of air, temperatures of less than -150 °C would be needed to produce dry ice snow in Antarctica. Antarctica is a frozen desert with little precipitation; the South Pole itself receives less than 10 cm (4 in) per year, on average. Temperatures reach a minimum of between −80 °C (−112 °F) and −90 °C (−130 °F) in the interior in winter and reach a maximum of between 5 °C (41 °F) and 15 °C (59 °F) near the coast in summer. Sunburn is often a health issue as the snow surface reflects almost all of the ultraviolet light falling on it. Given the latitude, long periods of constant darkness or constant sunlight create climates unfamiliar to human beings in much of the rest of the world.[48]

The snow surface at Dome CStation
is typical of most of the continent's surface.

East Antarctica is colder than its western counterpart because of its higher elevation.
Weather fronts
rarely penetrate far into the continent, leaving the center cold and dry. Despite the lack of precipitation over the central portion of the continent, ice there lasts for extended periods. Heavy snowfalls are common on the coastal portion of the continent, where snowfalls of up to 1.22 metres (48 in) in 48 hours have been recorded.

At the edge of the continent, strong
katabatic winds
off the polar plateau
often blow at storm force. In the interior, wind speeds are typically moderate. During clear days in summer, more solar radiation
reaches the surface at the South Pole than at the equator
because of the 24 hours of sunlight each day at the Pole.[1]

Antarctica is colder than the
Arctic
for three reasons. First, much of the continent is more than 3,000 m (9,800 ft) above sea level, and temperature decreases with elevation in the troposphere. Second, the Arctic Ocean covers the north polar zone: the ocean's relative warmth is transferred through the icepack and prevents temperatures in the Arctic regions from reaching the extremes typical of the land surface of Antarctica. Third, the Earth is at
aphelion
in July (i.e., the Earth is furthest from the Sun in the Antarctic winter), and the Earth is at perihelion
in January (i.e., the Earth is closest to the Sun in the Antarctic summer). The orbital distance contributes to a colder Antarctic winter (and a warmer Antarctic summer) but the first two effects have more impact.[49]

The
aurora australis, commonly known as the southern lights, is a glow observed in the night sky near the South Pole created by the plasma-full
solar winds
that pass by the Earth. Another unique spectacle is diamond dust, a ground-level cloud composed of tiny ice crystals. It generally forms under otherwise clear or nearly clear skies, so people sometimes also refer to it as clear-sky precipitation. A
sun dog, a frequent atmospheric
optical phenomenon, is a bright "spot" beside the true
sun.[48]

Several governments maintain permanent manned
research stations
on the continent. The number of people conducting and supporting scientific research and other work on the continent and its nearby islands varies from about 1,000 in winter to about 5,000 in the summer, giving it a population density
between 0.00007 inhabitants per square kilometre (0.00018/sq mi) and 0.00035 inhabitants per square kilometre (0.00091/sq mi) at these times. Many of the stations are staffed year-round, the winter-over personnel typically arriving from their home countries for a one-year assignment. An Orthodox church,
Trinity Church, opened in 2004 at the Russian
Bellingshausen Station
is also manned year-round by one or two priests, who are similarly rotated every year.[50][51]

The first semi-permanent inhabitants of regions near Antarctica (areas situated south of the
Antarctic Convergence) were British and American
sealers
who used to spend a year or more on South Georgia, from 1786 onward. During the
whaling
era, which lasted until 1966, the population of that island varied from over 1,000 in the summer (over 2,000 in some years) to some 200 in the winter. Most of the whalers were Norwegian, with an increasing proportion of Britons. The settlements included Grytviken,
Leith Harbour,
King Edward Point,
Stromness,
Husvik,
Prince Olav Harbour,
Ocean Harbour
and Godthul. Managers and other senior officers of the whaling stations often lived together with their families. Among them was the founder of Grytviken, Captain
Carl Anton Larsen, a prominent Norwegian whaler and explorer who, along with his family, adopted British citizenship in 1910.

The first child born in the
southern polar region
was Norwegian girl Solveig Gunbjørg Jacobsen, born in Grytviken on 8 October 1913, and her birth was registered by the resident British Magistrate of
South Georgia. She was a daughter of Fridthjof Jacobsen, the assistant manager of the whaling station, and Klara Olette Jacobsen. Jacobsen arrived on the island in 1904 and became the manager of Grytviken, serving from 1914 to 1921; two of his children were born on the island.[52]

Emilio Marcos Palma
was the first person born south of the 60th parallel south
(the continental limit according to the Antarctic Treaty),[53]
as well as the first one born on the Antarctic mainland, in 1978 at Base Esperanza, on the tip of the Antarctic Peninsula;[54][55]
his parents were sent there along with seven other families by the Argentine
government to determine if family life was suitable on the continent. In 1984, Juan Pablo Camacho was born at the Frei Montalva Station, becoming the first Chilean born in Antarctica. Several bases are now home to families with children attending schools at the station.[56]
As of 2009, eleven children were born in Antarctica (south of the 60th parallel south): eight at the Argentine Esperanza Base[57]
and three at the Chilean Frei Montalva Station.[58]

A census of sea life carried out during the
International Polar Year
and which involved some 500 researchers was released in 2010. The research is part of the global Census of Marine Life
(CoML) and has disclosed some remarkable findings. More than 235 marine organisms live in both polar regions, having bridged the gap of 12,000 km (7,456 mi). Large animals such as some cetaceans and birds make the round trip annually. More surprising are small forms of life such as mudworms, sea cucumbers
and free-swimming snails found in both polar oceans. Various factors may aid in their distribution – fairly uniform temperatures of the deep ocean at the poles and the equator which differ by no more than 5 °C, and the major current systems or marine conveyor belt
which transport egg and larva stages.[63]

About 400 species of lichen-forming fungi are known to exist in Antarctica.

About 1150 species of fungi have been recorded from Antarctica, of which about 750 are non-lichen-forming and 400 are lichen-forming.[64][65]
Some of these species are cryptoendoliths
as a result of evolution under extreme conditions, and have significantly contributed to shaping the impressive rock formations of the McMurdo Dry Valleys and surrounding mountain ridges. The apparently simple morphology, scarcely differentiated structures, metabolic systems and enzymes still active at very low temperatures, and reduced life cycles shown by such fungi make them particularly suited to harsh environments such as the McMurdo Dry Valleys. In particular, their thick-walled and strongly melanized cells make them resistant to UV-light. Those features are observed in different Antarctic fungi which can be shown by molecular studies to belong in different taxonomic orders. They can also be observed in algae and cyanobacteria, suggesting that these are adaptations to the conditions prevailing in Antarctica. This has led to speculation that, if life ever occurred on Mars, it might have looked similar to Antarctic fungi such as Cryomyces minteri.[66]
Some of these fungi are also apparently endemic to Antarctica. Endemic Antarctic fungi also include certain dung-inhabiting species which have had to evolve in response to the double challenge of extreme cold while growing on dung, and the need to survive passage through the gut of warm-blooded animals.[67]

The climate of Antarctica does not allow extensive vegetation to form. A combination of freezing temperatures, poor
soil
quality, lack of moisture, and lack of sunlight inhibit plant growth. As a result, the diversity of plant life is very low and limited in distribution. The flora
of the continent largely consists of bryophytes. There are about 100 species of
mosses
and 25 species of liverworts, but only two species of
flowering plants, both of which are found in the Antarctic Peninsula:
Deschampsia antarctica
(Antarctic hair grass) and Colobanthus quitensis
(Antarctic pearlwort). Growth is restricted to a few weeks in the summer.[64][68]

Seven hundred species of algae exist, most of which are
phytoplankton. Multicolored
snow algae
and diatoms
are especially abundant in the coastal regions during the summer.[68]
Bacteria have been found living in the cold and dark as deep as a half-mile deep under the ice.[69]

The dumping of waste (even old vehicles), such as here at the Russian Bellingshausen Station in 1992, is prohibited since the entry into force of the Protocol on Environmental Protection in 1998.

The Protocol on Environmental Protection to the Antarctic Treaty (also known as the Environmental Protocol or Madrid Protocol) came into force in 1998, and is the main instrument concerned with conservation and management of biodiversity in Antarctica. The Antarctic Treaty Consultative Meeting is advised on environmental and conservation issues in Antarctica by the Committee for Environmental Protection. A major concern within this committee is the risk to Antarctica from unintentional introduction of non-native species from outside the region.[70]

The passing of the
Antarctic Conservation Act
(1978) in the U.S. brought several restrictions to U.S. activity on Antarctica. The introduction of alien plants or animals can bring a criminal penalty, as can the extraction of any indigenous species. The overfishing
of krill, which plays a large role in the Antarctic ecosystem, led officials to enact regulations on fishing. The Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR), a treaty that came into force in 1980, requires that regulations managing all Southern Ocean fisheries consider potential effects on the entire Antarctic ecosystem.[1]
Despite these new acts, unregulated and illegal fishing, particularly of Patagonian toothfish
(marketed as Chilean Sea Bass in the U.S.), remains a serious problem. The illegal fishing of toothfish has been increasing, with estimates of 32,000 tonnes
(35,300 short tons) in 2000.[71][72]

29 National Antarctic Programs together supporting science in Antarctica (2009)

Antarctica has no government, although various countries claim sovereignty in certain regions. Although a few of these countries have mutually recognized each other's claims,[73]
the validity of these claims is not recognized universally.[1]

New claims on Antarctica have been suspended since 1959 and Antarctica is considered politically neutral. Its status is regulated by the 1959
Antarctic Treaty
and other related agreements, collectively called the Antarctic Treaty System. Antarctica is defined as all land and
ice shelves
south of 60° S for the purposes of the Treaty System. The treaty was signed by twelve countries including the Soviet Union
(and later Russia), the United Kingdom, Argentina,
Chile, Australia, and the United States.[74]
It set aside Antarctica as a scientific preserve, established freedom of scientific investigation and environmental protection, and banned military activity on Antarctica. This was the first arms control
agreement established during the Cold War.

In 1983, the Antarctic Treaty Parties began negotiations on a convention to regulate mining in Antarctica.[75]
A coalition of international organizations[76]
launched a public pressure campaign to prevent any minerals development in the region, led largely by Greenpeace International,[77]
which established its own scientific station–World Park Base–in the Ross Sea region[78]
and conducted annual expeditions to document environmental effects of humans on Antarctica.[79]
In 1988, the Convention on the Regulation of Antarctic Mineral Resources (CRAMRA) was adopted.[80]
The following year, however, Australia and France announced that they would not ratify the convention, rendering it dead for all intents and purposes. They proposed instead that a comprehensive regime to protect the Antarctic environment be negotiated in its place.[81]
The Protocol on Environmental Protection to the Antarctic Treaty (the 'Madrid Protocol') was negotiated as other countries followed suit and on 14 January 1998 it entered into force.[81][82]
The Madrid Protocol bans all mining in Antarctica, designating Antarctica a 'natural reserve devoted to peace and science'.

The Antarctic Treaty prohibits any
military activity in Antarctica, including the establishment of military bases and fortifications, military manoeuvers, and weapons testing. Military personnel or equipment are permitted only for scientific research or other peaceful purposes.[83]
The only documented military land manoeuvre was Operation NINETY
by the Argentine military.[84]

The areas shown as
Australia's
and New Zealand's
claims were British territory until they were handed over following the countries' independence. Australia currently claims the largest area. The claims of Britain, Australia, New Zealand, France and Norway are all recognized by each other.

Other countries participating as members of Antarctic Treaty have a territorial interest in Antarctica, but the provisions of the Treaty do not allow them to make their claims while it is in force.[89][90]

There is no economic activity in Antarctica at present, except for fishing off the coast and small-scale
tourism, both based outside Antarctica.

Although coal,
hydrocarbons, iron ore,
platinum,
copper,
chromium, nickel, gold and other minerals have been found, they have not been in large enough quantities to exploit. The 1991
Protocol on Environmental Protection to the Antarctic Treaty
also restricts a struggle for resources. In 1998, a compromise agreement was reached to place an indefinite ban on mining, to be reviewed in 2048, further limiting economic development and exploitation. The primary economic activity is the capture and offshore trading of fish. Antarctic fisheries in 2000–01 reported landing 112,934 tonnes.

Small-scale "expedition tourism" has existed since 1957 and is currently subject to Antarctic Treaty and Environmental Protocol provisions, but in effect self-regulated by the
International Association of Antarctica Tour Operators
(IAATO). Not all vessels associated with Antarctic tourism are members of IAATO, but IAATO members account for 95% of the tourist activity. Travel is largely by small or medium ship, focusing on specific scenic locations with accessible concentrations of iconic wildlife. A total of 37,506 tourists visited during the 2006–07 Austral summer
with nearly all of them coming from commercial ships. The number was predicted to increase to over 80,000 by 2010.[93][94]

There has been some concern over the potential adverse environmental and ecosystem effects caused by the influx of visitors. A call for stricter regulations for ships and a tourism quota has been made by some environmentalists and scientists.[95]
The primary response by Antarctic Treaty Parties has been to develop, through their Committee for Environmental Protection and in partnership with IAATO, "site use guidelines" setting landing limits and closed or restricted zones on the more frequently visited sites. Antarctic sight seeing flights (which did not land) operated out of Australia and New Zealand until the fatal crash of Air New Zealand Flight 901
in 1979 on Mount Erebus, which killed all 257 aboard. Qantas
resumed commercial overflights to Antarctica from Australia in the mid-1990s.

Antarctic fisheries in 1998–1999 (1 July – 30 June) reported landing 119,898 tonnes. Unregulated fishing landed five to six times more than the regulated fishery, and allegedly illegal fishing in Antarctic waters in 1998 resulted in the seizure (by France and Australia) of at least eight fishing ships. See
Ocean fisheries#Southern Ocean.

About 30 countries maintain about seventy
research stations
(40 year-round or permanent, and 30 summer-only) in Antarctica, with an approximate population of 4000 in summer and 1000 in winter.

Each year, scientists from 28 different nations conduct
experiments
not reproducible in any other place in the world. In the summer more than 4,000 scientists operate research stations; this number decreases to just over 1,000 in the winter.[1]McMurdo Station, which is the largest research station in Antarctica, is capable of housing more than 1,000 scientists, visitors, and tourists.

Researchers include
biologists,
geologists,
oceanographers,
physicists,
astronomers,
glaciologists, and
meteorologists. Geologists tend to study
plate tectonics, meteorites from
outer space, and resources from the breakup of the supercontinent
Gondwana. Glaciologists in Antarctica are concerned with the study of the history and
dynamics
of floating ice, seasonal snow,
glaciers, and
ice sheets. Biologists, in addition to examining the wildlife, are interested in how harsh temperatures and the presence of people affect adaptation and survival strategies in a wide variety of organisms. Medical physicians have made discoveries concerning the spreading of viruses and the body's response to extreme seasonal temperatures. Astrophysicists at
Amundsen–Scott South Pole Station
study the celestial dome and cosmic microwave background radiation. Many astronomical observations are better made from the interior of Antarctica than from most surface locations because of the high elevation, which results in a thin atmosphere, low temperature, which minimizes the amount of water vapour in the atmosphere, and absence of
light pollution, thus allowing for a view of space clearer than anywhere else on Earth. Antarctic ice serves as both the shield and the detection medium for the largest
neutrino telescope
in the world, built 2 km (1.2 mi) below Amundsen-Scott station.[97]

Since the 1970s, an important focus of study has been the
ozone layer
in the atmosphere
above Antarctica. In 1985, three British scientists working on data they had gathered at Halley Station
on the Brunt Ice Shelf
discovered the existence of a hole in this layer. It was eventually determined that the destruction of the ozone was caused by chlorofluorocarbons
emitted by human products. With the ban of CFCs in the Montreal Protocol
of 1989, climate projections indicate that the ozone layer will return to 1980 levels between 2050 and 2070.[98]

In September 2006,
NASA
satellite data revealed that the Antarctic ozone hole
was larger than at any other time on record, 27.5 million km2
(10.6 million sq mi).[99]
The impacts of the depleted ozone layer on climate changes occurring in Antarctica are not well understood.[98]

In 2007,
The Polar Geospatial Center
was founded. The Polar Geospatial Center uses geospatial
and remote sensing
technology to provide mapping services to American federally funded research teams. Currently, the Polar Geospatial Center can image all of Antarctica at 50 cm resolution every 45 days.[100]

Meteorites
from Antarctica are an important area of study of material formed early in the solar system; most are thought to come from
asteroids, but some may have originated on larger
planets. The first meteorite was found in 1912, and named the
Adelie Land meteorite. In 1969, a Japanese expedition discovered nine meteorites. Most of these meteorites have fallen onto the ice sheet in the last million years. Motion of the ice sheet tends to concentrate the meteorites at blocking locations such as mountain ranges, with wind erosion bringing them to the surface after centuries beneath accumulated snowfall. Compared with meteorites collected in more temperate regions on Earth, the Antarctic meteorites are well-preserved.[103]

This large collection of meteorites allows a better understanding of the abundance of meteorite types in the solar system and how meteorites relate to asteroids and comets. New types of meteorites and rare meteorites have been found. Among these are pieces blasted off the Moon, and probably Mars, by impacts. These specimens, particularly
ALH84001
discovered by ANSMET, are at the center of the controversy about possible evidence of microbial life on Mars. Because meteorites in space absorb and record cosmic radiation, the time elapsed since the meteorite hit the Earth can be determined from laboratory studies. The elapsed time since fall, or terrestrial residence age, of a meteorite represents more information that might be useful in environmental studies of Antarctic ice sheets.[103]

In January 2013, an 18 kg (40 lb) meteorite was discovered frozen in ice on the Nansen ice field by a Search for Antarctic Meteorites, Belgian Approach (SAMBA) mission.[105]

In January 2015, reports emerged of a 2 kilometres (1.2 mi)
circular structure, supposed a meteorite crater, on the surface snow of
King Baudouin Ice Shelf. Satellite images from 25 years ago seemingly show it.

Due to its location at the South Pole, Antarctica receives relatively little solar radiation. This means that it is a very cold continent where water is mostly in the form of ice. Precipitation is low (most of Antarctica is a
desert) and almost always in the form of snow, which accumulates and forms a giant ice sheet which covers the land. Parts of this ice sheet form moving glaciers known as
ice streams, which flow towards the edges of the continent. Next to the continental shore are many
ice shelves. These are floating extensions of outflowing glaciers from the continental ice mass. Offshore, temperatures are also low enough that ice is formed from
seawater
through most of the year. It is important to understand the various types of Antarctic ice to understand possible effects on sea levels and the implications of global cooling.

Sea ice extent expands annually in the Antarctic winter and most of this ice melts in the summer. This ice is formed from the ocean water and floats in the same water and thus does not contribute to rise in sea level. The
extent
of sea ice
around Antarctica has remained roughly constant in recent decades, although the thickness changes are unclear.[106][107]

Melting of floating ice shelves (ice that originated on the land) does not in itself contribute much to sea-level rise (since the ice displaces only its own mass of water). However it is the outflow of the ice from the land to form the ice shelf which causes a rise in global sea level. This effect is offset by snow falling back onto the continent. Recent decades have witnessed several dramatic collapses of large ice shelves around the coast of Antarctica, especially along the Antarctic Peninsula. Concerns have been raised that disruption of ice shelves may result in increased glacial outflow from the continental ice mass.[108]

On the continent itself, the large volume of ice present stores around 70% of the world's fresh water.[32]
This ice sheet is constantly gaining ice from snowfall and losing ice through outflow to the sea. Overall, the net change is slightly positive at approximately 33Gt/year[109]
with significant regional variation. West Antarctica is currently experiencing a net outflow of glacial ice, which will increase global sea level over time. A review of the scientific studies looking at data from 1992 to 2006 suggested that a net loss of around 50 gigatonnes
of ice per year was a reasonable estimate (around 0.14 mm of sea level rise).[110]
Significant acceleration of outflow glaciers in the Amundsen Sea Embayment
may have more than doubled this figure for 2006.[111]

East Antarctica is a cold region with a ground base
above sea level
and occupies most of the continent. This area is dominated by small accumulations of snowfall which becomes ice and thus eventually seaward glacial flows. The mass balance of the East Antarctic Ice Sheet
as a whole is thought to be slightly positive (lowering sea level) or near to balance.[110][111][112]
However, increased ice outflow has been suggested in some regions.[111][113]

Some of Antarctica has been warming up; particularly strong warming has been noted on the Antarctic Peninsula. A study by Eric Steig published in 2009 noted for the first time that the continent-wide average surface temperature trend of Antarctica is slightly positive at >0.05 °C (0.09 °F) per decade from 1957 to 2006. This study also noted that West Antarctica has warmed by more than 0.1 °C (0.2 °F) per decade in the last 50 years, and this warming is strongest in winter and spring. This is partly offset by fall cooling in East Antarctica.[114]
There is evidence from one study that Antarctica is warming
as a result of human carbon dioxide
emissions.,[115]
but this remains ambiguous.[116]
The amount of surface warming in West Antarctica, while large, has not led to appreciable melting at the surface, and is not directly affecting the West Antarctic Ice Sheet's contribution to sea level. Instead the recent increases in glacier outflow are believed to be due to an inflow of warm water from the deep ocean, just off the
continental shelf.[117][118]
The net contribution to sea level from the Antarctic Peninsula is more likely to be a direct result of the much greater atmospheric warming there.[119]

In 2002 the Antarctic Peninsula's
Larsen-B
ice shelf collapsed.[120]
Between 28 February and 8 March 2008, about 570 square kilometres (220 sq mi) of ice from the Wilkins Ice Shelf
on the southwest part of the peninsula collapsed, putting the remaining 15,000 km2
(5,800 sq mi) of the ice shelf at risk. The ice was being held back by a "thread" of ice about 6 km (4 mi) wide,[121][122]
prior to its collapse on 5 April 2009.[123][124]
According to NASA, the most widespread Antarctic surface melting of the past 30 years occurred in 2005, when an area of ice comparable in size to California briefly melted and refroze; this may have resulted from temperatures rising to as high as 5 °C (41 °F).[125]

A study published in
Nature Geoscience
in 2013 (online in December 2012) identified central West Antarctica as one of the fastest-warming regions on Earth. The researchers present a complete temperature record from Antarctica's Byrd Station and assert that it "reveals a linear increase in annual temperature between 1958 and 2010 by 2.4±1.2 °C".[126]

Each year a large area of low ozone concentration or "ozone hole" grows over Antarctica. This hole covers almost the whole continent and was at its largest in September 2008, when the longest lasting hole on record remained until the end of December.[127]
The hole was detected by scientists in 1985[128]
and has tended to increase over the years of observation. The ozone hole is attributed to the emission
of chlorofluorocarbons
or CFCs into the atmosphere, which decompose the ozone
into other gases.[129]

Some scientific studies suggest that ozone depletion may have a dominant role in governing climatic change in Antarctica (and a wider area of the Southern Hemisphere).[128]
Ozone absorbs large amounts of ultraviolet radiation in the stratosphere. Ozone depletion over Antarctica can cause a cooling of around 6 °C in the local stratosphere. This cooling has the effect of intensifying the westerly winds which flow around the continent (the
polar vortex) and thus prevents outflow of the cold air near the South Pole. As a result, the continental mass of the East Antarctic ice sheet is held at lower temperatures, and the peripheral areas of Antarctica, especially the Antarctic Peninsula, are subject to higher temperatures, which promote accelerated melting.[128]
Models also suggest that the ozone depletion/enhanced polar vortex effect also accounts for the recent increase in sea-ice just offshore of the continent.[130]

Jump up
^The word was originally pronounced without the first
/k/, but the
spelling pronunciation
has become the standard. The "c" was originally added to the spelling for etymological reasons and then began to be pronounced.[3][4]

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^"Antarctica's geology". Royal Geographical Society (with the Institute of British Geographers) in partnership with the British Antarctic Survey and the Foreign and Commonwealth Office. Retrieved
31 October
2014.

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^Rogan-Finnemore, Michelle (2005). "What Bioprospecting Means for Antarctica and the Southern Ocean". In Von Tigerstrom, Barbara.
International Law Issues in the South Pacific. Ashgate Publishing. p. 204.
ISBN0-7546-4419-7.
"Australia, New Zealand, France, Norway and the United Kingdom reciprocally recognize the validity of each other's claims." – Google Books link: [1]

Jump up
^Morris, Michael (1988).
The Strait of Magellan. Martinus Nijhoff Publishers. p. 219.
ISBN0-7923-0181-1. Retrieved
21 October
2010.
...Brazil has even designated a zone of Antarctic interest that overlaps the Argentine sector but not the Chilean one...

^
Jump up to:
ab"Antarctica".
The World Factbook. United States Central Intelligence Agency. 2011. Retrieved
22 October
2011.
...the US and Russia reserve the right to make claims...

Jump up
^National Aeronautics and Space Administration, Advanced Supercomputing Division (NAS) (26 June 2001).
"The Antarctic Ozone hole". Government of the United States.
Archived
from the original on 15 February 2009. Retrieved
7 February
2009.